Primary focus of proposed studies is detailed analysis of (autogenous) repression of splicing of the primary transcript of a presumptive regulatory gene, suppressor-of-white-apricot [su(wa)], by the protein product of that gene. Various studies are proposed including refinement of observations implicating the 3' splice site region of the regulated intron as the target for autorepression of splicing; in vitro splicing and binding studies to establish and characterize direct interaction between the su(wa) protein and primary transcript; and attempt (with Dr. Ann L. Beyer) to visualize splicing and autorepression of splicing of su(wa) transcripts in the electron microscope; and analysis of an unusual domain of the su(wa) protein which strongly resembles a domain in a second splicing regulator (the tra protein) with the objective of determining whether these domains are diagnostic of splicing regulators. Further, we propose to extend our analysis of the su(wa) promoter. Among other things these studies are expected, first, to provide the first documented case of a conventional enhancer core element in an arthropod and, second, to allow the construction of a maternal deposition vector system allowing specific, high level delivery of mRNAs (and proteins) from cloned genes to young embryos. This vector would have various important general applications including to analysis of embryonic pattern formation. If appropriate studies above are successful, they will result in a general strategy for molecular analysis of splicing regulation. Specifically, the maternal deposition vector should allow high level deposition of any cloned splicing regulator in young embryos. Young embryos, in turn, are appropriate material for electron microscopic visualization of splicing and splicing regulation as well as for preparation of nuclear splicing extracts for in vitro splicing studies.